The present invention provides topical therapeutic compositions for accelerating wound healing comprising mammalian IL-1 proteins.
Interleukin-1 (IL-1) refers to a family of polypeptides which are secreted by macrophages and certain other cell types in response to immunogenic and traumatic stimulation. IL-1 proteins have been associated with a complex spectrum of biological activities, and appear to play a primary role in initiating host response to injury and infection. IL-1 is a primary immunostimulatory signal capable of inducing thymocyte proliferation via induction of interleukin-2 release, and stimulating proliferation and maturation of B lymphocytes. In addition, IL-1 has been linked with prostaglandin production, inflammation, and induction of fever.
A review of the literature relating to IL-1 by Oppenheim et al., Immunol. Today 7: 45 (1986), reported that "IL-1 has multiple effects on cells involved in inflammation and wound healing." As shown by the disclosures of the following references, IL-1 is known to stimulate proliferation of fibroblasts and attract cells involved in the inflammatory response.
Postlethwaite et al., J. Exp. Med. 155: 801 (1983) described experiments which indicated that IL-1-like molecules were capable of stimulating fibroblast proliferation in vitro and also the release of collagenase by cultured fibroblasts.
Luger et al., J. Immunol. 131: 816 (1983), Sauder et al., J. Immunol. 132: 828 (1984), and several papers appearing in Kluger et al., eds., The Physiologic, Metabolic, and Immunologic Actions of Interleukin-1, (Alan R. Liss, Inc., New York, 1985; hereinafter cited as "Kluger Symposium") describe factors derived from human epidermal cells, designated epidermal cell thymocyte-activating factor (ETAF) and leukocytic pyrogen (LP), which appeared to be biochemically similar to IL-1. These factors were active as chemoattractants for polymorphonuclear (PMN) and mononuclear leukocytes (MNL). Since many inflammatory skin conditions are characterized by infiltration of PMN and MNL into the dermis, the authors suggested that ETAF, and possibly IL-1, played a role in the pathogenesis of inflammatory skin diseases. Gahring et al., in another paper published in the Kluger Symposium, supra, found measurable levels of ETAF in the strateum corneum, the outermost layer of the skin, and speculated that the presence of the factor in the strateum corneum provided a mechanism for immediate deposition of ETAF in a wound site and subsequent induction of inflammation.
Byars et al., Fed. Proc. 43: 426 (1984) found that supernatants of guinea pig macrophage cultures stimulated with muramyl dipeptide (MDP) were capable of inducing proliferation of capillary endothelial cells. However, the authors did not demonstrate that IL-1 in the culture supernatants was the mitogenic factor.
Bevilaqua et al., J. Exp. Med. 160: 618 (1984) described experiments in which partially purified IL-1 preparations were shown to induce procoagulant activity in cultures of human vascular endothelial cells.
Human IL-1 activity resides in two distantly related proteins, which are now known as IL-1.alpha. and IL-1.beta. (March et al., Nature 315: 641 (1985)). Both molecules are normally synthesized as larger precursors having molecular weights of about 31,000 daltons, which are subsequently processed by proteolytic cleavage to yield mature forms having molecular weights of approximately 17,500 daltons. Although the proteins share only 26% homology, both molecules bind to the same cell surface receptor and in initial experiments appeared to possess coextensive biological activity. Recently, cDNA, coding for both human IL-1 species have been cloned and expressed in E. coli, which has enabled production of sufficient quantities of IL-1.alpha. and IL-1.beta. for clinical evaluation.
However, the clinical utility of direct IL-1 application in aiding the process of wound healing has never been established. Due to the diversity of biological activities which have been attributed to IL-1, and the lack of understanding of the role of such activities in the healing process, the present state of the art does not allow one to predict whether IL-1 would retard or accelerate wound healing if applied topically to the site of injury.
It has now been found that IL-1 proteins are effective promoters of wound healing when applied to injuries in the form of a topical formulation comprising the protein.